(i) Field to which the Invention Relates
The present invention is with respect to a process and apparatus for producing a valve part, such as a valve seat or valve moving member, for a cone labyrinth valve.
(ii) The Prior Art
Designs for cone labyrinth valves had been put forward in U.S. Pat. No. 3,185,438 and German Pat. No. 2,008,765. The valve parts, that is to say the valve moving member and the valve seat, of such a labyrinth valve are each made with at least two blade-like edges in the form of annular cones, such that on the valve member being moved towards the valve seat the blade-like edges are responsible for producing a complexly folded or labyrinth-like path for the fluid to be rate-controlled and/or shut down. The fluid may for example be a liquified gas, melted metal, suspensions of solids and the like. When the valve is shut, it is cleaned at the same time, because any grain or hair-like materials in the fluid, for example in a liquid, are cut off and scraped from the valve member and valve seat and for this reason cleared from the system or cut down in size and will furthermore be cleared from the valve between the valve member and the valve seat later on. The form of the blade-like edges on the valve member and the valve seat may be the same in the two cases (see U.S. Pat. No. 3,185,438) or different (see German Pat. No. 2,008,765); furthermore the properties of the materials used for making the valve member and the valve seat may be different. Because of the different form and/or different material of the valve parts, the meshing and rate-controlling properties of the edges on the valve member and valve seat may be changed so that the best valve properties are produced in any given case of use.
The valve member and valve seat of such a cone labyrinth valve may be produced in a number of different ways, for example by pressure casting, in a powder metallurgical process, by extruding etc. with later machining for truing up the edges. As a general rule however, the valve member or the valve seat is machined from solid material on a lathe and then after-processed in a special spinning and polishing operation to get an accurate size. Because the depth of the valleys between one edge and the next one on the valve member and on the valve seat are relatively great in size, and because narrow spaces between the edges or ring cones may only be machined with very thin lathe cutting tools, producing such valve members and valve seats is generally a very complex operation. Furthermore the sizes and spacings of the different parts of such a valve member and more specially with respect to conicity, the depth of the cutting edges and the spacing therebetween have to be kept within tight tolerances, although once the valve member and valve seat are put into operation and the valve shut, there will be a self-truing or positioning effect. Even so however such prior art processes are generally complex and high in price.
Furthermore machining and processing have to be so exact that on shutting the labyrinth valve the valve member and the valve seat are such that their edges are run up against each other at more or less the same time or with a cutting effect, that is to say the "drawing cut" takes place on shutting down the valve (see German Pat. No. 2,008,765, column 4, starting at line 51).
A suggestion has been made for the valve plate and the valve seat of such cone labyrinth valves to have their edges on separate rings. Although in this case the edges of the valve bodies no longer have to be turned from solid material, it has turned out to be hard to get the rings with the edges exactly into the right position and leveled up in relation to each other that the properties noted or tolerances are kept to on shutting down the valve. More specially in the case of small sizes of valve members very exact measuring instruments have been necessary and in fact in some cases later machining and truing up of the edges has been necessary for producing the right cone angle and depth of edge.